You might recognize this as "The Kiss", but the official name of this iconic photo is "V-J Day in Times Square".  

They had just announced Victory in Japan and the war - the entire war - was officially over (Germany had surrended months earlier, in May).  A sailor grabbed a nurse and in the excitement of the day, planted a big ole kiss on her.  A photographer from LIFE magazine (Alfred Eisenstaedt) happened to be nearby and captured the moment.

For all you trivia fans, there's a book, "The Kissing Sailor" and the authors determined that the sailor was George Mendonsa and the nurse was Greta Zimmer Friedman.  

Happy Fourth!